Equation for counting boxes used. Please help!!!!

I work at a packaging company and Im trying to impress my boss by creating a spreadhseet that can calculate how many boxes will be needed to pack an order. Any help would be greatly appreciated. I need help creating a excel spread sheet that will give box sizes a value. Then the quantity ordered be divided by the value for each of the four box sizes. Then the decimal left over be converted to a whole number. Then all numbers of each box size combined. I know it is confusing but I know what Im trying to do. I just dont know what formulas to use. If you are willing to help, I can explain further. Thank you.